Cast component and method for the production thereof

ABSTRACT

The invention relates to a method for the production of a cast component made of an aluminium diecasting alloy, in which the cast component is subjected to a heat treatment process after casting, wherein an aluminium diecasting alloy is used, by means of which the cast component has an elongation at break A 5  of ≧10% and a yield point Rp 0.2  of &lt;120 MPa, and wherein a single-step annealing process for stability is carried out at a temperature of 120-260° C., after which the heat-treated cast component has a break at elongation A 5  of ≧7% and a yield point Rp 0.2  of ≧110 MPa. Furthermore, the invention relates to a cast component which is produced in accordance with a method of this type.

The present invention relates to a method for producing a cast component made of an aluminium diecasting alloy of the type disclosed in the preamble of claim 1. The invention further relates to a cast component made of an aluminium diecasting alloy of the type disclosed in the preamble of claim 11.

In order for cast components of this type made of aluminium diecasting alloys to be used, for example, in the automobile industry, they are currently normally subjected to a heat treatment process after primary forming and casting.

As a result of this heat treatment a cast component is produced, by means of which short-term heat stability at 205° C. over a period of 1 hour, for example, or long-term heat stability at 150° C. over a period of 1,000 hours, for example, may be achieved. In this case, short-term heat stability is necessary for the car body to be appropriately heat-stable, for example, when baking on a layer of paint, this process taking place over 20 mins at 170° C. for example. Long-term heat stability is necessary, for example, so the components can withstand corresponding temperatures which are emitted by the motor, for example during vehicle operation, or which act on the components by way of solar radiation.

In this case, crash-sustainable cast components with reduced ductility may be produced, for example, which have a yield point Rp_(0.2) of, for example, between 120 and 165 MPa and an elongation at break A₅ of ≧7%. Corresponding components with a suitable level of ductility are thus produced and may be used, for example, in the region of a deformable zone.

Nowadays, in order to be able to produce these components, alloys must be used, for example, which contain a high proportion of the alloy elements Ti, Zr and Mo. However, these alloy elements are extremely expensive and therefore the cast components are ultimately also very expensive.

The object of the present invention is therefore to provide a method and a cast component of the aforementioned type, by means of which cost-effective production can be achieved.

This object is achieved in accordance with the invention by a method and cast component having the features of claims 1 and 11. Advantageous embodiments with useful and non-trivial developments of the invention are disclosed in the respective dependent claims.

In order to provide a method by means of which cast components with an elongation at break A₅ of ≧7% and a yield point Rp_(0.2) of ≧110 MPa can be produced as cost-effectively as possible, it is provided in accordance with the invention to use an aluminium diecasting alloy, by means of which the cast component, as cast, has an elongation at break A₅ of ≧10% and a yield point Rp_(0.2) of <120 MPa, the cast component being subjected to an annealing process for stability at a temperature of 120 to 260° C. after primary forming. By way of the said annealing process for stability, a correspondingly suitable aluminium diecasting alloy may thus be used in a simple manner so sufficient values are still obtained after the heat treatment.

These sufficient values are necessary to produce aluminium diecasting components having suitable properties so they can be used, for example in the region of deformable zones, within the field of automobile manufacture. As is comprised within the scope of the invention, it should also be noted, however, that the present cast component is in no way limited to use within the region of deformable zones of a motor vehicle. The present cast component may also be used at other locations, for example in the region of the chassis or in the region of external attaching parts or components.

The present invention makes it possible to achieve a sufficient level of heat stability of the cast component in a simple manner in such a way that said component remains heat-stable in the short-term for 1 hour at 205° C. and in the long-term for 1,000 hours at 150° C. without any significant change to the mechanical properties, such as the elongation at break A₅ and the yield point Rp_(0.2).

A particularly cost-effective aluminium diecasting alloy can thus be produced which comprises <8.5% by weight, and in particular ≦8.3% by weight silicon. This reduced silicon content in the diecasting alloy may, in particular, be compensated by an optimised content of magnesium.

In a further embodiment of the invention it has proved to be advantageous if the magnesium content is <0.6% by weight, and in particular ranges from 0.02 to 0.3% by weight. The aforementioned properties of the aluminium diecasting alloy thus enable production which is as cost-effective as possible, in which the necessary values of the cast component, in particular after heat treatment, are attained without having to add a considerable amount of Ti, Zr or Mo for example.

In a further embodiment of the invention, it has also proved to be advantageous if an aluminium diecasting alloy having the following alloy elements is used:

  4 to 8.2 % by weight silicon 0.5 to 0.6 % by weight manganese 0.15 to 0.2  % by weight iron 0.04 to 0.2  % by weight magnesium 0.04 to 0.08 % by weight titanium 14 * 10⁻³ to 18 * 10⁻³ % by weight strontium (140-180 ppm) and the rest being formed of aluminium, which individually contains a maximum of 0.05% and a total maximum of 0.2% by weight impurities caused by the production method.

An aluminium diecasting alloy of this type is thus characterised not only by an extremely low silicon content and an optimised magnesium content, but in particular in that the alloy elements Ti, Zr and Mo can be dispensed with in most cases. These alloy elements in particular are influential, namely since they drive up the price of aluminium diecasting alloys.

In a further embodiment of the invention it has also proved to be advantageous if an aluminium diecasting alloy is used, by means of which the cast component, as cast, has an elongation at break A₅ of ≧11%, and in particular ≧12%. It should thus be ensured that the cast component also has a sufficient elongation at break A₅ of ≧7% after the heat treatment or annealing process for stability.

In order to produce a cast component which has a particularly advantageous elongation at break A₅, even after the heat treatment, an aluminium diecasting alloy is preferably used, by means of which the cast component, as cast, has an elongation at break A₅ of ≧13%.

It is further advantageous to use an aluminium diecasting alloy, by means of which the cast component, as cast, has a yield point Rp_(0.2) of ≧105, and in particular of ≧110 MPa. Starting from this yield point Rp_(0.2) it is thus possible to achieve a required yield point Rp_(0.2) of ≧120 MPa after heat treatment in a simple manner.

In order to obtain an even higher yield point after the annealing process for stability, it has also proved advantageous to set the magnesium content of the aluminium diecasting alloy within a range of up to 0.6% by weight at most, the cast component, as cast, comprising a yield point Rp_(0.2) of ≧80 and in particular of ≧85 MPa.

In a further embodiment of the invention, it has also proved advantageous if the annealing process for stability is carried out at a temperature of 200 to 240° C. It is thus possible to achieve a particularly quick annealing process, the duration of which is, for example, <180 mins, and in particular <60 mins.

In particular, the annealing process for stability is ultimately carried out in such a way that the heat-treated cast component subsequently has a yield point Rp_(0.2) of ≧115 to ≦220 MPa, and in particular ≧125 to ≦165 MPa. Particularly advantageous components may thus be obtained which, for example, may be used in the body work of passenger vehicles.

Of course, the aforementioned advantages discussed in conjunction with the method according to the invention also apply to the cast component according to claim 11.

Further advantages, features and details of the invention will be disclosed in the following description of preferred embodiments.

EXAMPLE 1

In accordance with Example 1, an aluminium diecasting alloy is used which comprises the following alloy elements:

7.8 to 8.2 % by weight silicon 0.5 to 0.6 % by weight manganese 0.15 to 0.2  % by weight iron 0.04 to 0.08 % by weight magnesium 0.04 to 0.08 % by weight titanium 14 * 10⁻³ to 18 * 10⁻³ % by weight strontium (140-180 ppm) and the rest being formed of aluminium, which individually contains a maximum of 0.05% and a total maximum of 0.2% by weight impurities caused by the production method.

This aluminium diecasting alloy is characterised in that it has a break at elongation A₅ of ≧10% and a yield point Rp_(0.2) of <120 MPa after the cast component has been cast or primary formed and is immediately in the cast state.

The components produced from the aforementioned aluminium diecasting alloy are subsequently subjected to an annealing process for stability at between 120 and 260° C., and in particular between 200 to 240° C. for a duration of <180 mins, for example approximately 20 mins to 90 mins, and in particular for a duration of 30 mins to 60 mins.

After the heat treatment, the cast component has a yield point Rp_(0.2) of, for example, approximately 110 to 120 MPa, and in particular between 115 to 118 MPa.

EXAMPLE 2

According to Example 2, an aluminium diecasting alloy for the cast components is used, which has the following alloy elements:

7.8 to 8.2 % by weight silicon 0.5 to 0.6 % by weight manganese 0.15 to 0.2  % by weight titanium 0.08 to 0.12 % by weight magnesium 0.04 to 0.08 % by weight titanium 14 * 10⁻³ to 18 * 10⁻³ % by weight strontium (140-180 ppm) and the rest being formed of aluminium, which individually contains a maximum of 0.05% and a total maximum of 0.2% by weight impurities caused by the production method.

The aluminium diecasting alloy used in this case has an elongation at break A₅ of ≧10% and a yield point Rp_(0.2) of <120 MPa as cast.

The respective cast component as cast is subsequently subjected to an annealing process for stability at a temperature of, for example, approximately 120 to 260° C., and in particular at a temperature of 200 to 240° C. within a period of <180 mins, for example approximately 20 mins to approximately 90 mins, and in particular within a period of approximately 30 mins to approximately 60 mins.

The cast component subsequently has an elongation at break A₅ of ≧7% and a yield point of Rp_(0.2), for example, approximately 125 to 135 MPa, and in particular of 129 to 133 MPa.

EXAMPLE 3

According to Example 3, an aluminium diecasting alloy for the respective cast component is used which comprises the following alloy elements:

7.8 to 8.2 % by weight silicon 0.5 to 0.6 % by weight manganese 0.15 to 0.2  % by weight iron 0.12 to 0.16 % by weight magnesium 0.04 to 0.08 % by weight titanium 14 * 10⁻³ to 18 * 10⁻³ % by weight strontium (140-180 ppm) and the rest being formed of aluminium, which individually contains a maximum of 0.05% and a total maximum of 0.2% by weight impurities caused by the production method.

The cast components produced using the aforementioned aluminium diecasting alloy have an elongation at break A₅ of ≧10% and a yield point Rp_(0.2) of <120 MPa as cast, i.e. before any heat treatment.

The individual cast components are in turn subjected to an annealing process for stability carried out at a temperature ranging from 120 to 260° C., and in particular from 200 to 240° C. The annealing process for stability is carried out over a period of up to 180 mins, and in this case, for example, approximately 20 mins to 90 mins, and in particular over a period from 30 to 60 mins.

The cast components heat-treated in this manner have, after the annealing process for stability, an elongation at break A₅ of ≧7% and a yield point Rp_(0.2) ranging between 135 and 150 MPa, and in particular ranging from 141 to 148 MPa.

EXAMPLE 4

According to Example 4, an aluminium diecasting alloy is used which comprises the following alloy elements:

7.8 to 8.2 % by weight silicon 0.5 to 0.6 % by weight manganese 0.15 to 0.2  % by weight iron 0.16 to 0.2  % by weight magnesium 0.04 to 0.08 % by weight titanium 14 * 10⁻³ to 18 * 10⁻³ % by weight strontium (140-180 ppm) and the rest being formed of aluminium, which individually contains a maximum of 0.05% and a total maximum of 0.2% by weight impurities caused by the production method.

In the present case also, the cast components produced by the aforementioned aluminium diecasting alloy comprise a elongation at break A₅ of ≧7% and a yield point Rp_(0.2) of <120 MPa as cast and before the heat treatment.

The cast components are in turn subjected to an annealing process for stability at a temperature of 120 to 260° C., and in particular between 200 and 240° C. The annealing process for stability is thus carried out within a period lasting up to 180 mins, in particular lasting between 20 mins and 90 mins, and in particular within a period lasting between 30 mins and 60 mins.

In the present case, cast components are thus produced which, after the heat treatment, have a break at elongation A₅ of ≧7% and a yield point Rp_(0.2) ranging from 145 to 165 MPa, and in particular ranging from 151 to 161 MPa.

SUMMARY

All in all, it can thus be seen from the above Examples 1 to 4 that, in the present case, starting from respective cast components which have an elongation at break A₅ of ≧10% and a yield point Rp_(0.2) of <120 MPa as cast and before heat treatment, heat-treated cast components can be produced by way of a suitable annealing process for stability, which cast components subsequently have an elongation at break A₅ of ≧7% and a yield point Rp_(0.2) of ≧110 MPa.

It can further be seen that, by adjusting the magnesium content, the yield point can be adjusted to the values given according to Examples 1 to 4, depending on the field in which the respective cast component is to be used. For a high yield point, magnesium content may be adjusted to a maximum of 0.6% by weight.

It can also be seen from Examples 1 to 4 that the respective single-step annealing process for stability is, in this case, carried out at a temperature ranging from 120 to 260° C., and in particular ranging from 200 to 240° C. The shortest possible annealing process for stability is thus achieved, in which it is ensured that for all cast component samples the required short-term heat stability or long-term stability is obtained without having to excessively or considerably reduce the yield point Rp_(0.2).

A single-step annealing process for stability of this type with temperatures within the disclosed temperature range, and in particular <240° C., may also be carried out during the painting process for example, in particular during the paint baking process of a motor vehicle. An annealing process for stability of this type at such temperatures, i.e. for example a temperature of <240° C. for a duration of <180 mins, and in particular <60 mins, also has the advantage that the cast components are not distorted and can be heat-treated in a large batch in a batch furnace.

A particular advantage when using the cast component, for example within the field of vehicle manufacture, also lies in that the cast component as cast, i.e. when it has minimum strength (Rp_(0.2) approx. 100 MPa) and maximum ductility (A₅ approx. 10 to 14%), can be mechanically joined, for example riveted. During the subsequent heat treatment, which, for example, may be carried out during the painting or paint baking process of the vehicle body at, for example approximately 180° C. for a period of approximately 30 mins, the final mechanical values are set. 

1. Method for producing a cast component made of an aluminium diecasting alloy, in which the cast component is subjected to a heat treatment process after casting, characterised in that an aluminium diecasting alloy is used, by means of which the cast component, as cast, has an elongation at break A₅ of ≧10% and a yield point RP_(0.2) of <120 MPa, and in that an annealing process for stability is carried out at a temperature of 120-260° C., after which the heat-treated cast component has an elongation at break A₅ of ≧7% and a yield point Rp_(0.2) of ≧110 MPa.
 2. Method according to claim 1, characterised in that an aluminium diecasting alloy with <8.5% by weight, and in particular ≦8.3% by weight silicon is used
 3. Method according to claim 1, characterised in that an aluminium diecasting alloy with <0.6% by weight, and in particular 0.02-0.3% by weight magnesium is used.
 4. Method according to claim 1, characterised in that an aluminium diecasting alloy with the following alloy elements is used:   4 to 8.2 % by weight silicon 0.5 to 0.6 % by weight manganese 0.15 to 0.2  % by weight iron 0.04 to 0.2  % by weight magnesium 0.04 to 0.08 % by weight titanium 14 * 10⁻³ to 18 * 10⁻³ % by weight strontium (140-180 ppm)

and the rest being formed of aluminium, which individually contains a maximum of 0.05% and a total maximum of 0.2% by weight impurities caused by the production method.
 5. Method according to claim 1, characterised in that an aluminium diecasting alloy is used, by means of which the cast component, as cast, has an elongation at break A₅ of ≧11%, and in particular of ≧12%.
 6. Method according to of claim 1, characterised in that an aluminium diecasting alloy is used, by means of which the cast component, as cast, has an elongation at break A₅ of ≧13%.
 7. Method according to claim 1, characterised in that an aluminium diecasting alloy is used, by means of which the cast component, as cast, has a yield point Rp_(0.2) of ≧105, and in particular of ≧110 MPa.
 8. Method according to claim 1, characterised in that an aluminium diecasting alloy is used, by means of which the cast component, as cast, has a yield point Rp_(0.2) of ≧115, and in particular of ≧120 MPa.
 9. Method according to claim 1, characterised in that the annealing process for stability is carried out at a temperature of 200-240° C.
 10. Method according to claim 1, characterised in that the annealing process for stability is carried out, after which the heat-treated cast component has a yield point Rp_(0.2) of ≧115 to ≦165 MPa, and in particular ≧125 to ≦220 MPa.
 11. Cast component made of an aluminium diecasting alloy and subjected to a heat treatment process after casting, characterised in that the cast component is formed from an aluminium diecasting alloy which, as cast, has an elongation at break A₅ of ≧10% and a yield point Rp_(0.2) of <120 MPa, in that the cast component is subjected to an annealing process for stability at a temperature of 120-260° C., after which the heat-treated cast component has a break at elongation A₅ of ≧7% and a yield point Rp_(0.2) of ≧110 MPa.
 12. Cast component according to claim 11, characterised in that the aluminium diecasting alloy of the cast component comprises <8.5% by weight, and in particular ≦8.3% by weight silicon.
 13. Cast component according to claim 11, characterised in that the aluminium diecasting alloy of the cast component comprises <0.6% by weight, and in particular 0.02-0.3% by weight magnesium.
 14. Cast component according to claim 11, characterised in that the aluminium diecasting alloy of the cast component comprises the following alloy elements:   4 to 8.2 % by weight silicon 0.5 to 0.6 % by weight manganese 0.15 to 0.2  % by weight iron 0.04 to 0.2  % by weight magnesium 0.04 to 0.08 % by weight titanium 14 * 10⁻³ to 18 * 10⁻³ % by weight strontium (140-180 ppm)

and the rest being formed of aluminium, which individually contains a maximum of 0.05% and a total maximum of 0.2% by weight impurities caused by the production method.
 15. Cast component according to claim 11, characterised in that the cast component, as cast, has an elongation at break A₅ of ≧11%, and in particular of ≧12%.
 16. Cast component according to claim 11, characterised in that the cast component, as cast, has an elongation at break A₅ of ≧13%.
 17. Cast component according to claim 11, characterised in that the cast component, as cast, has a yield point Rp_(0.2) of ≧105, and in particular of ≧110 MPa.
 18. Cast component according to claim 11, characterised in that the cast component, as cast, has a yield point Rp_(0.2) of ≧115, and in particular of ≧120 MPa.
 19. Cast component according to claim 11, characterised in that the cast component is subjected to an annealing process for stability at a temperature of 200-240 ° C.
 20. Cast component according to claim 11, characterised in that the heat-treated cast component has a yield point Rp_(0.2) of ≧115 to ≦220 MPa, and in particular ≧125≦165 MPa. 